Grand Street Campus center fielder Williams Jerez, a 6-foot-4 prospect who credited his development to the experience he garnered playing for the summer team sponsored by Hank Steinbrenner, joined the enemy yesterday.

The Red Sox took Jerez in the second round (81st overall) of the First-Year Player Draft — seven picks before the Yankees’ next choice — making him the city’s highest selection out of high school in 15 years. In 1996, Tottenville pitcher Jason Marquis was chosen No. 35 by the Braves.

“I feel proud,” Jerez told The Post through a translator. “A lot of kids dream about this opportunity and my dream has come true.”

Jerez migrated to New York City from Santo Domingo, Dominican Republic, two years ago. Last summer he hooked up with Hank’s Yanks, and 18-and-under team for underprivileged youth, and his stock shot up with impressive performances in showcases.

He followed that up with a memorable senior year at Grand Street, helping the Wolves reach the PSAL Class A semifinals by hitting .692 with five home runs, 32 RBIs and 26 stolen bases.

Jerez opened the Red Sox eyes during a workout at Fenway Park last Thursday in which general manager Theo Epstein was present.

It was thought the Yankees were intent on taking Jerez early on after having scouts follow him around much of the spring.

Jerez, who has committed to JUCO powerhouse San Jacinto College (Texas) but likely is to sign with the Red Sox, said he was thrilled to be taken so high. So was Ray Negron, his coach with Hank’s Yanks and a senior advisor with the Bombers.

“I’ll be rooting for him to make it to the Major Leagues,” Negron said. “But I’m a Yankee fan. So if [he does make it and faces the Yankees], I’ll have to root for whoever is pitching that day to strike him out.”